Blinking question mark on folder on white screen at startup

A Few weeks ago when I was overseas my computer just decided to not start up. Nothing happened to it physically. I can get it to the blinking question mark on the folder or the Internet recovery with the globe but nothing past that. Two days ago I got it on (not sure how) and I was using my computer normally. I decided to try to update my OS to Yosemite since someone told me the problem may be out of date OS. After the restart it went back to before- white screen with blinking question mark. Haven't been able to get in since then. Any suggestions on how to fix this before I take it into a store or pay for Apple Support???

PS- I'm really not sure what OS I had before I tried to update but I know I haven't updated in a long time.